Electric gaseous discharge device



Nov. 8, 1938. w. HNLEIN ET AL l 2,135,662

ELECTRIC GAS-EOUS DISCHARGE DEVICE Filed June 27, 1956 uw ...fr .fm n Y .m aKnm OH .R m n^CO Er T Wea A :Hm awww Y WHB Patented Nov. 8, 1938 UNI-TED STATES I 2,135,662 ELECTRIC GA'sEoUs DISCHARGE DEVICE Walter Hnlen, Berlin-Haselhorst, and Hermann Kreit, Berlin-Friedrichshagen, Germany, assignors to General Electric Company, a corporation of New York Application 'June 27, 1936, Serial No. 87,770

. In Germany July 12, 1935 1 Claim.

The present invention relates to electric gaseous discharge devices generally, and more particularly' to vapor arc devices which operate at relatively high intensities.

A particular object of the invention is to provide a high intensity gaseous discharge lamp which will Yhave a long useful life. Another object of the invention is to eliminate the blackening of the lamp envelope. Another object of the invention is to provide a high intensity lamp in which the radiations of caesium arev added to those of mercury. Still other objects andadvantages of the invention will appear from the following.detailed'specifcation or from an inspection of the accompanying drawing.

The invention consists in a new and novel com.

bination of elements, as hereinafter set fort and claimed.

It has been proposed to modify the light emitted by high intensity mercury vapor arc lamps by admixing caesium with the mercury,

these lamps at temperatures of the order of 500 C. or more. At lsuch high temperatures it has been found that there is appreciable blackening of the lamp envelope where -any of the usual glasses of the'prior art are used, due to the fact that duringJ operation of the lamp the caesium reacts with the component parts of the glass.

.We have now found that these mercurycaesium lampsvcan be operated without anyl appreciable blackening provided a novel glass of our inventionA is used for the lamp envelope. This novel glass has a silica content amountingto only 25 to 40%, a boric oxide content of 10 to 20%, an alumina content of 25 to 35% and an earth alkali oxide content of 20 to 40%. Furthermore the sum of the silicav and the boric oxide should not amount to more than 50% of the entire composition. We have found that high intensity v,mercury vapor lamps having envelopes consisting of such a glass are not only subjected to no blackening during operation' but are also resistant to reduction by the caesium vapor even at the high operating temperatures. ide and barium oxide are preferably used as the earth alkali oxides in this glass, but where desired they are partially replaced by magnesium oxide an'd zinc oxide.

The proportion of caesium added to the mercury is ordinarily of the order of 0.2 to 5%, but in some cases, as Where the lamp is operated at an especially high temperature, the caesium is introduced in proportions as high as 12%, in which case the caesium radiation becomes espe- Calcium oxcially strong in relation to the mercury radiation. It as been found that even with the largerof these caesiuxn additions, and with the correspondingly higher temperature of the discharge vessel which is necessary therewith, no blackening of the lamp envelope occurs either as a result of the discharge itself or as a result of the chemical influence of the caesium vapor.

'Ihis novel glass of our invention has a low coefficient of expansion, and at the same time has a high softening temperature, in excess of that required by thel operating temperatures of the vInercury-caesium lamp.

For the purpose of illustrating our invention We have shown an elevational view, in part section, of a preferred embodiment thereof in the accompanying drawing.

As shown in this drawing our novel lamp has a tubular'envelope I lled with any suitable gas or vapor or ymixtures thereof. For example, We have',obtained;` excellent results using argon at a pressure of the order of 5 mm. of mercury, together with just enough mercury to provide sub-y stantially atmospheric pressure when it is all evaporated Mixed with this mercury is a small quantity of caesium, of theorder of 0.2 to 5%, or in some cases as much as 12%, of the mercury. Surrounding said envelope I thereis' a tubular jacket 2. The space between the envelope I and the jacket 2 is either evacuated or filled with an indifferent gas, such as nitrogen, at any suitable pressure, such as half an atmosphere. The jacket 2 has 'at one end thereof a stem 3, through the pinch 4 of Which two current inleads 5 and 6 are sealed. The current inlead 5 is flexibly connected to the inlead 1 .which is fused into the adjacent end of the envelope I. carries at its-inner endfa thermionic cathode 8, while a second thermionic cathode 9 is carried by an inlead I0 which is sealed through the opposite end of the envelope I. These thermionic electrodes 8 and 9 can be of any desired type and composition, .but I prefer to use a wound Said inlead 'l tungsten helix, as shown, within which there' is retained a rod 8 and 9', respectively, of electron emitting material, such as a sintered mixture of parts of barium oxide and calcium oxide with I0 parts of tungsten, since such an electrode has been found to be exceptionally effective in my novel'lamp. Dished metal rings il and I2 are tted against the ends of the envelope I, and are held in this position by Vmeans of rigid longitudinal wires I3 and I4 which unite'them with each other. These wires I3 and I4, which together with the rings II and I2 f'orm a stiff frame surrounding the envelope I, are anchored in the pinch 4. The wire I4 is 4in practice made an extension of the inlead 6, and the lower end thereof is flexibly connected with the inlead I0, so that this wire also serves to conduct the current to the thermionic cathode 9. Each metal ring Il and I2 has a plurality of spring lingers l5 axed to the outside thereof which bear against the inner wall of the jacket 2, and thus serve to prevent lateral displacement of the envelope l. A screw base 22 is rmly attached to the jacket 2 by means of the clamping band 23, leads 5 and '6 being connected to the tip 2d and sleeve 25 thereof, respectively.

The glass of the envelope I is preferably a glass of special-composition which We have discovered resists blackening when subjected to a high temperature mercury-caesium discharge. This glass contains 25 to. 40% silica, 10 to 20% boric oxide, 25 to 35% alumina and 20 to 40% earth alkali oxide, the sum of the silica and the boric oxide in all cases being less than 50%. Such a glass has a low coeicient of expansion and is likewise resistant to chemical attack by either mercury vapor or caesium vapor, even at temperatures considerably in excess of 500 C., so that no blackening of the envelope is produced by these vapors during operation of the lamps. A glass of the following composition has proved This glass has a softening temperature considerably in excess of that required by any of these lamps, so that .a discharge at several atmospheres pressure can be operated in a lamp constructed thereof without damage.

While We have described our invention as embodied in a lamp having an envelope consisting of our novel glass composition, it is to be understood that this glass may likewise be used to ilash the inside of envelopes of other composition having a suitable coecient of expansion and transformation point. It is likewise to be understood that various other changes, modiiications and substitutions, Within the scope of the appended v having the following composition:

Percent SiOz 35 B201 A1203 30 CaO 15 BaO WALTER HERMANN KREFFI. 

